[turbofan] Initial version of the new LoadElimination.

test/unittests/compiler/load-elimination-unittest.cc

-// Copyright 2014 the V8 project authors. All rights reserved.
+// Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "src/compiler/load-elimination.h"
 #include "src/compiler/access-builder.h"
-#include "src/compiler/load-elimination.h"
+#include "src/compiler/node.h"
 #include "src/compiler/simplified-operator.h"
 #include "test/unittests/compiler/graph-unittest.h"
 #include "test/unittests/compiler/node-test-utils.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 class LoadEliminationTest : public TypedGraphTest {
  public:
   LoadEliminationTest() : TypedGraphTest(3), simplified_(zone()) {}
   ~LoadEliminationTest() override {}
 
  protected:
-  Reduction Reduce(Node* node) {
-    // TODO(titzer): mock the GraphReducer here for better unit testing.
-    GraphReducer graph_reducer(zone(), graph());
-    LoadElimination reducer(&graph_reducer, graph(), simplified());
-    return reducer.Reduce(node);
+  void Run() {
+    LoadElimination load_elimination(graph(), zone());
+    load_elimination.Run();
   }
 
   SimplifiedOperatorBuilder* simplified() { return &simplified_; }
 
  private:
   SimplifiedOperatorBuilder simplified_;
 };
 
-
-TEST_F(LoadEliminationTest, LoadFieldWithStoreField) {
-  Node* object1 = Parameter(Type::Any(), 0);
-  Node* object2 = Parameter(Type::Any(), 1);
-  Node* value = Parameter(Type::Any(), 2);
+TEST_F(LoadEliminationTest, LoadFieldAndLoadField) {
+  Node* object = Parameter(Type::Any(), 0);
   Node* effect = graph()->start();
   Node* control = graph()->start();
+  FieldAccess access = {kTaggedBase,
+                        kPointerSize,
+                        MaybeHandle<Name>(),
+                        Type::Any(),
+                        MachineType::AnyTagged(),
+                        kNoWriteBarrier};
+  Node* load1 = effect = graph()->NewNode(simplified()->LoadField(access),
+                                          object, effect, control);
+  Node* load2 = effect = graph()->NewNode(simplified()->LoadField(access),
+                                          object, effect, control);
+  control = graph()->NewNode(common()->Return(), load2, effect, control);
+  graph()->end()->ReplaceInput(0, control);
 
-  FieldAccess access1 = AccessBuilder::ForContextSlot(42);
-  Node* store1 = graph()->NewNode(simplified()->StoreField(access1), object1,
-                                  value, effect, control);
-  Reduction r1 = Reduce(graph()->NewNode(simplified()->LoadField(access1),
-                                         object1, store1, control));
-  ASSERT_TRUE(r1.Changed());
-  EXPECT_EQ(value, r1.replacement());
+  Run();
 
-  FieldAccess access2 = AccessBuilder::ForMap();
-  Node* store2 = graph()->NewNode(simplified()->StoreField(access2), object1,
-                                  object2, store1, control);
-  Reduction r2 = Reduce(graph()->NewNode(simplified()->LoadField(access2),
-                                         object1, store2, control));
-  ASSERT_TRUE(r2.Changed());
-  EXPECT_EQ(object2, r2.replacement());
+  EXPECT_THAT(graph()->end(), IsEnd(IsReturn(load1, load1, graph()->start())));
+}
 
-  Node* store3 = graph()->NewNode(
-      simplified()->StoreBuffer(BufferAccess(kExternalInt8Array)), object2,
-      value, Int32Constant(10), object1, store2, control);
+TEST_F(LoadEliminationTest, StoreFieldAndLoadField) {
+  Node* object = Parameter(Type::Any(), 0);
+  Node* value = Parameter(Type::Any(), 1);
+  Node* effect = graph()->start();
+  Node* control = graph()->start();
+  FieldAccess access = {kTaggedBase,
+                        kPointerSize,
+                        MaybeHandle<Name>(),
+                        Type::Any(),
+                        MachineType::AnyTagged(),
+                        kNoWriteBarrier};
+  Node* store = effect = graph()->NewNode(simplified()->StoreField(access),
+                                          object, value, effect, control);
+  Node* load = effect = graph()->NewNode(simplified()->LoadField(access),
+                                         object, effect, control);
+  control = graph()->NewNode(common()->Return(), load, effect, control);
+  graph()->end()->ReplaceInput(0, control);
 
-  Reduction r3 = Reduce(graph()->NewNode(simplified()->LoadField(access1),
-                                         object2, store3, control));
-  ASSERT_FALSE(r3.Changed());
+  Run();
 
-  Reduction r4 = Reduce(graph()->NewNode(simplified()->LoadField(access1),
-                                         object1, store3, control));
-  ASSERT_TRUE(r4.Changed());
-  EXPECT_EQ(value, r4.replacement());
+  EXPECT_THAT(graph()->end(), IsEnd(IsReturn(value, store, graph()->start())));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8